Capacitive touch switches sense a change in electrical capacitance at electrodes, for example, when approached by a human finger, and use that sensing to generate an electrical switch signal.
Unlike conventional mechanical switches with movable contacts, including membrane switches, capacitive touch switches have no moving parts and are particularly well-suited to applications where there is mechanical shock and long life is required. Because capacitive sensing operates over a distance, capacitive touch switches can be easily sealed from environmental contaminants such as dirt or water by a protective barrier. In particular, capacitive touch switches may be placed behind a panel, for example, of nonconductive plastic or glass, to provide an unbroken, attractive surface resistant to damage.
Incorporating capacitive touch switches into a product normally requires a significant amount of custom engineering to develop the sensing electrode array, the necessary mounting structure for the sensing array and the layout of the electronic circuit which is desirably positioned close to the electrodes for maximum sensitivity. The cost of this effort can be an obstacle to the adoption of capacitive touch switch systems. Because the electrodes are normally tightly integrated with the sensing surface, it can be difficult to repair or rework a capacitive touch switch.